Actually it was not started by the Greenies...It was started by the American Farm Bureau, the National Corn Growers Association and a company called Broin Companies, which has since changed its name to Poet Energy.
For a long time if one did the energetic calculations on a calorie in vs. calorie out, it took more energy to make a gallon of ETOH than you got back out. Nothing there has changed much, although the ETOH guys have improved their efficiencies a bit.
Then under some political pressure from the above mentioned groups and some land grant university profs who get their funding from guess who...the US Dept of Agriculture changed their calculations and guess what??? Now instead of ETOH being a net loss, it is a net positive!! Wowsers, changed the First Law of Thermodynamics...That my friends is pretty dang good!!
Also, at the time there was concern about a gasoline oxygenater called MTBE getting out into the ground water. This is an important concern and must be dealt with, however in my view ETOH is the wrong solution.
Taking gallons of high energy diesel fuel to grow and transport corn, fertilizer, produce the fertilizer etc to produce a medium energy compound like ETOH makes no sense. Not to mention the huge CO2 production associated with ETOH fermentation, some of which is now trapped but lots of which is released into the atmospher...Can you say Global Warming??